Users of trolleys frequently experience that their manoeuvring can be problematic. When pushing or pulling them uphill, or even when carrying heavy loads on a substantially flat surface, users may experience heavy stress. Likewise when pushing trolleys downhill, it may take considerable force to prevent the trolley from coming loose and picking up speed. Many times it is difficult or impossible to pull or push a trolley with the body in an ergonomically correct or non-hurting position, or the user of a trolley may not be strong enough to maintain such a position.
In particular for children's trolleys and transport trolleys for liquid samples, such as for use within the medical or pharmaceutical industries, the security risks are considerable if a user of such a trolley is unable to hold the trolley and it comes loose.
It is also desirable to be able to push or pull such a trolley using less effort in general, by the trolley being self-propelled to decrease the necessary pushing force.
For children's trolleys and transport trolleys for liquid samples, there is also a desire to be able to rock the transported child or liquid samples—in the former case in order to sooth the child, in the latter for instance to keep the samples from settling. It is desirable that such rocking is possible using different rocking programs, so that a suitable rocking movement can be selected depending on the circumstances.
Concurrently, there is a need to provide a disengaged, free-wheeling operation mode, in which the trolley acts as a conventional non-motorized, wheeled trolley, for instance when the user wishes to have more exercise, or when manoeuvring in small spaces.
All these aims should be achieved using a simple, robust yet energy-efficient construction, offering both flexibility and the highest security standards, at the same time as the trolly assembly should be environmentally friendly and cost-efficient to produce.
Numerous self-propelled trolleys have been proposed, offering solutions to subsets of said problems. Some of these include U.S. Pat. No. 8,499,898 B2, disclosing a children's trolley with a speed control; WO 2014013482 A1, disclosing a rocking functionality for use with a children's trolley; U.S. Pat. Nos. 5,937,961 and 8,033,348 B1, disclosing a respective disconnectable motor for a trolley; and EP 2019016 A2, showing a motor arranged at a driven shaft.